My experience is that air conditioning is pretty easily accommodated. In my D’s college if a person who required A/C (ex. for asthma or something) was placed in a building without central A/C the college would simply install a window unit in the room – this way there was no issue in terms of the student requiring a specific dorm or rooming with whoever he/she chose. My D’s sophomore roommate required A/C and one was installed in their room by the college. They did not move ahead of the line in terms of room selection due to her roommate’s accommodation and there was no issue with them being roommates.
If it is something that may be more limited such needing as a wheelchair accessible room my guess is that the college would have to be sure that every student who needs such a room is accommodated before a person could pull in a roommate.
Again this is something I would ask each college you are looking at. You can email the Office of Disabilities and/or the Office of Residential Life.